Three brain injury patients diagnosed as being in a vegetative
state—meaning they do not respond to their environment—may actually be
conscious. Using EEG (electroencephalography) to measure their brain
activity, researchers found that the patients could follow simple
commands.

Mind reading: Using EEG to measure brain activity, researchers
found that some patients diagnosed as being in a vegetative state could
respond to simple commands. The pattern of electrical activity in these
patients (one example is shown above) is identical to patterns seen in
healthy people.

This supports previous findings
from the same group suggesting that some people who appear outwardly
unresponsive may have a relatively high level of cognitive capacity.
Researchers aim to ultimately develop the approach into a communication
tool.

In the study, researchers examined 16 patients with brain injury—some
due to traumatic injury and others due to lack of oxygen—and 12 healthy
people, asking both groups to imagine moving either their hands or toes
while wearing an EEG monitor. They found that, like the healthy people,
three of the brain injury patients could reliably generate two distinct
brain activity patterns based on the command. One patient did it more
than 200 times, which is even more than the healthy participants
managed.

The team had previously used functional MRI, or brain imaging, to
show that a patient diagnosed as being in a vegetative state could use a
similar system to answer yes or no questions. That startling finding
rocked the medical world, begging the question of how many of these
patients had cognitive function beyond what their outward function
indicated.

MRI machines are, however, expensive and largely limited to
hospitals, making them a difficult tool to study brain injury patients,
who are often in rehabilitation or nursing homes. In the new study,
researchers used a standard EEG device, which is relatively inexpensive
and highly portable. "It's probably about as sensitive as MRI," says Adrian Owen,
a researcher at the University of Western Ontario, who led the study.
"That means we have something we can get out into the community and use
in hospitals or residential homes."

The researchers can detect when someone is thinking about moving a
hand versus a toe because the brain activity originates in a different
part of the motor cortex, the part of the brain that controls movement.
Owen's team spent much of the last year working out how to accurately
decode the electrical signals the brain emits when imaging these
movements. The findings of the new study were published this week in The Lancet.

The three patients who could respond via EEG did not share any
obvious features; they varied in age, in time since the original injury,
and in the type of injury suffered. Owen's team is now using
high-resolution functional MRI machines to study these patients' brains
in fine detail in hopes of finding some commonality. "Anything we can do
to improve our understanding or to learn more about catastrophic brain
injuries can help us understand what's going on," says Owen.

They hope to eventually use the EEG setup to ask patients questions,
which had been possible with functional MRI. At the moment, researchers
can't read the EEG response in real time, making interaction very
difficult. "Our priority now is trying to speed it up; then we'll move
on to communication," he says.

What exactly the new findings indicate about the patients' level of
consciousness is still controversial. "I think they were entirely aware
and conscious of what's going on," says Owen. "For them to do this, they
have to have understood the instructions we gave them, to have
sustained attention, to keep on task, and to respond. These are all
things we associated with consciousness."

Morten Storm Overgaard,
head of the Cognitive Neuroscience Research Unit at Aalborg University
in Denmark, disagrees. "I think their study is very interesting, but
it's hard to argue that there is a link between command-following and
consciousness. And there's no independent way of making sure," says
Overgaard, who wrote a commentary accompanying the paper. Overgaard does
agree, however, that someone who can reliably answer questions via
brain activity is likely conscious.

Both Overgaard and Owen say a new classification system is required
to accurately reflect the state these patients are in. "While they do
meet all the clinical criteria for the vegetative state, we know they
are not actually vegetative," says Owen. One suggestion that has yet to
catch on is "behavioral unresponsiveness syndrome."